I have confirmed that the image linked above works. If it still doesn’t work for you after going through the imaging process again, I would begin to think that your RPi 3 may have broken. You could perhaps try installing the official Raspbian image to verify what the issue is. I have had an RPi working fine for a long time, then after a simple reboot, it would not work. The ACT light just stayed lit like you describe, even with the sd card image verified to be correct on another working RPi. I ascribed the issues with that unit to ESD damage.